Car wont start...tried to jump start while wires were crossed...changed alternator fuse...but still wont start, completed dead, but lights , radio and etc all comes on

red is hot and black is ground never switch the two around , put them back the way they where and if your battery is going dead because of to much voltage drawn then you need to up the battery size and alternator .

There is a large maxi-fuse between the battery and alternator. Its at least 100 amp or more. It may be in the cable at the battery, or in one of the fuse boxes.
You may also have damaged the key switch or the brake circuit.
You may have to get a book to get the wiring diagrams to check everything involved.

it is the alternator . once a car has started the alternator runs the car

Might need to check the main circuits for a blown fuse or fuseable link.
There is a fuse wire between the alternator and battery.

The stall in reverse is most likely unrelated to your problem, unless your alternator went bad, and your battery is discharged. Try charging/replacing your battery. A jump start may not work as Dodge trucks don't like to idle well with a weak battery. Then try starting again, if it runs check the voltage at the battery. You should have 13-14.5 volts, if not you have a dead alternator. If it still won't start, please post some more details.

Hook the battery up or try to jump-start backwards did we?
The ECU fuse gets it's power from the 140 Amp (or 180 Amp, depending on which engine your vehicle is equipped with) ALTERNATOR fuse in the engine compartment fuse block.

you need to check your fuse you may have blown it

Your system probably has a lot of relays and other electronics that are bad now. Your Electronic Control Unit (ECU) may be cooked as well. You may also have a fusable link that has been blown as well. The fusable link is basicly an in-line fuse that you have to replace the wire to replace the fuse. Get a wiring schematic and look to see if theres a fuse or similar that you misssed. You may find that you dont have power going to all or part of one of your fuse panels.

Hope this helps...

You more than likely burned the fuse for the car's radio and will likely need to be replaced.

Always clean the battery terminals before jumping. An extremely dead battery may not accept a jump as it serves as a 'buffer" instead of helping. If you do get it started, charge battery with a battery charger then have alternator and battery tested for proper operation and check belt condition and tension as well.